I just picked up a 5V Adafruit Trinket and want to follow along with the tutorial in the learning section. Although It says it only works with the 3V version, can I add additional components to make the 5V Trinket work?

In theory, yes. Without extra parts it may be possible to power the 5V trinket from a 3v3 supply by bypassing the regulator and powering it with 3v3 directly through the 5V pin. But you’d be playing with fire.

Plugging in the USB port while this is set up would be bad news and potentially result in crispy fried Pi.

This would also mean you couldn’t use the Trinket’s onboard regulator to produce a decent operating current, so you would be limited in what you could run from it.